Always treat the hint chars' case as-is

Always treat the hint chars' case as-is

Since filtering hint markers by element text isn't available for the
`eb` command, the hint chars were previously treated as case insensitive
for that command. Similarly, they were also treated as case insensitive
when disabling the `hints.match_text` option.

However, the above led to numerous bugs. This commit simply gets rid of
that behavior, and keeps the hint chars consistent across all `f`
commands and options instead.